Device for controlling a kiln shut-off mechanism

ABSTRACT

A device for controlling a mechanism which is adapted to interrupt the electrical heating circuit of a kiln; the mechanism being of the type which includes a pivotally mounted rod having the inner end thereof extending into a kiln and being operative upon downward movement of said inner end to interrupt the electrical heating circuit of the kiln. The device is a fusible pryometric member adapted to be held in the path of downward movement of the inner rod end to prevent such movement until the interior of the kiln has been exposed to a predetermined amount of heating. The member has means, such as a uniform transverse cross-section or a notch in which the inner rod end is engageable, to accurately regulate the amount of heating required to cause deformation of the member.

[ 1 Sept. 24, 1974 DEVICE FOR CONTROLLING A KILN SHUT-OFF MECHANISM [75]Inventor: Milan Vukovich, Jr., Galena, Ohio [73] Assignee: The EdwardOrton, Jr. Ceramic Foundation, Columbus, Ohio 22 Filed: Jan. 12, 1970 21Appl. No.: 2,310

[56] References Cited UNITED STATES PATENTS 9/1938 Co Van et al. t73/358 2,675,600 4/1954 Dawson 337/416 X 3,287,530 11/1966 Dawson337/416 X FOREIGN PATENTS OR APPLICATIONS 8,426 4/1898 Great Britain337/401 Primary ExaminerHarold Broome Assistant Examiner-Fred E. BellAttorney, Agent, or Firm-Schuyler, Birch, Swindler, McKie and Beckett[57] ABSTRACT A device for controlling a mechanism which is adapted tointerrupt the electrical heating circuit of a kiln; the mechanism beingof the type which includes a pivotally mounted rod having the inner endthereof extending into a kiln and being operative upon downward movementof said inner end to interrupt the electrical heating circuit of thekiln. The device is a fusible pryometric member adapted to be held inthe path of downward movement of the inner rod end to prevent suchmovement until the interior of the kiln has been exposed to apredetermined amount of heating. The member has means, such as a uniformtransverse cross-section or a notch in which the inner rod end isengageable, to accurately regulate the amount of heating required tocause deformation of the memher.

5 Claims, 6 Drawing Figures nmmsmmm $838,377

HO 4 INVENTOR MILAN VUKOVICH, JR.

,1 .Ac M1 ATTORNEYS DEVICE FOR CONTROLLING A KILN SHUT-OFF MECHANISMBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to mechanisms for automatically interrupting the electricalheating circuit of a kiln, and specifically to an improved device forcontrolling such mechanisms.

2. Description of the Prior Art Ceramic artists and hobbyists commonlyuse prometric cones for controlling the firing of ceramic products in akiln. Such cones are composed of fusible ceramic material, and uponexposure to a predetermined amount of heating partially liquefy anddeform, thus providing a visual indication of the completion of firing.The operator, upon observing deformation of the cone, manuallyinterrupts the electrical heating circuit of the kiln. This method forcontrolling the firing of ceramic products, while operable, requiresthat the operator observe the interior of the kiln continuously duringthe critical period near the end of firing. Moreover, due to the intenseheat generated within the kiln, accurate observation of cone deformationis often precluded.

Shut-off mechanisms have been developed for automatic'ally interruptingthe electrical heating circuit of a kiln after the interior of the kilnhas been exposed to a predetermined amount of heating, i.e., uponcompletion of firing. Mechanisms of this type are disclosed in DawsonUS. Pat. Nos. 2,675,600 and 3,287,530. Such mechanisms employ amechanical system of rods, levers and switches, and a heat sensitiveelement for con trolling the movement of the various elements comprisingthe system. The heat sensitive element generally is a conventionalpyrometric cone which is positioned in the path of movement of one ofthe elements of the system, usually an end of a pivotally mounted rod,to prevent movement of such element until the interior of the kiln hasbeen exposed to a predetermined amount of heating. The principal reasonfor employing pyrometric cones as the heat sensitive control element inkiln shutoff mechanisms is because such cones are sensitive not only totemperature but also to time of exposure; the combined effect of theseparameters generally being referred to as the amount of heating. Thus,since ceramic products also are sensitive to temperature and time ofexposure, and consequently the firing thereof is a function of amount ofheating, pyrometric cones provide definite advantages over pyrometersand like devices which are sensitive to temperature only for controllingkiln shut-off mechanisms.

Several problems, however, attend the use of conventional pyrometriccones as the heat sensitive control element'in kiln shut-off mechanisms.Conventional pyrometric cones generally are shaped as truncatedtriangular pyramids, having three longitudinally extending, taperedsides. As used in kiln shut-off mechanisms, a cone is held by twohorizontally extending supporting strips which contact one of thelongitudinally extending sides of the cone near the top and bottomthereof. One end of a downwardly biased rod, comprising'one of theelements of the mechanical system of the shut-off mechanism, generallyengages the central portion of the edge of the cone opposite the sidethereof contacted by the supporting strips. Upon exposure of theinterior of the kiln to a predetermined amount of heating, the conepartially liquefies and deforms, permitting the rod end to movedownwardly and initiate the movements of the various elements comprisingthe mechanical system. I

Due to the relatively small cross-sectional area of the cone near thetop thereof, the transverse bending force applied to the cone by the rodend can result in premature deformation or even fracturing of the cone.Also, and perhaps more significantly, since the transversecross-sectional area of the cone varies continuously from the bottom tothe top thereof, lateral placement of the cone on the supporting stripsis critical for achieving the desired firing. For example, it has beenfound that lateral displacement of the cone by as little as one-eighthinch can result in maximum firing temperature variations of as much as10F. Thus, the artist or hobbyist must position the cone very carefullyon the supporting strips if underor over-firing is to be avoided.

A further difficulty in the use of conventional pyrometric cones in kilnshut-off mechanisms derives from the fact that the cones are composed offusible ceramic material which liquefies when exposed to a predeterminedamount of heating. Such liquefaction can result in adherence of theliquefied materials to the elements of the shut-off mechanism whichcontact the cone, i.e., the supporting strips and rod end.

SUMMARY OF THE INVENTION The device of the present invention obviatesthe problems described above with respect to the use of conventionalpyrometric cones as the heat sensitive control element for kiln shut-offmechanisms. The device of the invention is adapted to be used forcontrolling kiln shut-off mechanisms of the type which include a rodadapted to extend through a wall of a kiln with the inner end thereofextending into the kiln and the outer end thereof extending out of thekiln, mounting means pivotally supporting the rod intermediate saidends, biasing means urging the inner rod end downwardly, supportingmeans positioned below the inner rod end for holding the device of theinvention in the path of downward movement of said inner end, retainingmeans attached to the outer rod end, actuating means engageable by theretaining means when the device prevents downward movement of the innerrod end and releasable by the retaining means when the device permitsdownward movement of said inner end, and a switch contactable by theactuating means for interrupting the electrical heating circuit of thekiln when the actuating means is released by the retaining means.Basically described, the device comprises, a pyrometric member composedof fusible ceramic material and having means for accurately regulatingthe amount of heating required to cause deformation of the member sothat upon exposure of the member to said amount of heating, the memberwill at least partially liquefy and deform, permitting the inner rod endto move downwardly under the influence of the biasing means, therebycausing the electrical heating circuit of the kiln to be interrupted.

The regulating means may be comprised by the pyrometric member having auniform transverse crosssection so that irrespective of the lateralplacement of the member on the supporting means of the shut-offmechanism, the member will deform upon exposure to a predeterminedamount of heating.

The regulating means also may be comprised by one or more transverselyextending notches in the pyrometric member which are adapted to engagethe inner end of the shut-off mechanism rod. The notch or notcheseliminate errors in the lateral placement of the member with respect tothe supporting means and inner rod end. Moreover, by employing aplurality of such notches controlled variations in the amount of heatingrequired to cause deformation of the member may be achieved utilizing aparticular ceramic material and member configuration.

The transverse cross-sectional area of all embodiments of the pyrometricmember is large enough to eliminate premature deformation of themembers.

Also, preferably, the portions of the member which contact thesupporting means and inner rod end of the shut-off mechanism are coatedwith a refractory material to prevent adherence of the ceramic materialto the elements of the shut-off mechanism when the member liquifies uponexposure to heating.

With the foregoing in mind, it is a primary object of the presentinvention to provide an improved device for controlling a mechanismadapted to interrupt the electrical heating circuit of a kiln.

It is also an object of the invention to provide a device as describedin the preceding object, which device comprises a pyrometric membercomposed of fusible ceramic material.

It is an additional object of the invention to provide a device asdescribed in the preceding object, wherein the member has means foraccurately regulating the amount of heating required to causedeformation of the member.

It is a further object of the invention to provide a device as describedin the preceding objects, which device is both easy to use and reliable.

These and other objects of the invention will become apparent upon aconsideration of the detailed description of the preferred embodimentsthereof given in connection with the following drawings, wherein likereference numerals identify like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of atypical kiln shut-off mechanism in which the device of the invention isadapted to be employed;

FIG. 2 is a perspective view of a first embodiment of the device of theinvention;

FIG. 3 is a sectional view taken on line 3 3 of FIG.

FIG. 4 is a perspective view of a second embodiment of the device of theinvention;

FIG. 5 is a perspective view of a third embodiment of the device of theinvention; and

FIG. 6 is an elevational view of a fourth embodiment of the device ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical kiln shut-offmechanism is shown in FIG. 1, as designated by reference numeral 10.Mechanism 10 is of the type described in Dawson U.S. Pat. No. 2,675,600,and generally includes a rod 12 adapted to extend through a wall of akiln. Within the kiln wall, rod 12 is surrounded by a sleeve 14 having aplate 16 affixed to the inner end thereof, and a plate 18 affixed to theouter end thereof. Plates l6 and 18 abut the inner and outer surfaces,respectively, of the kiln wall. The inner end of rod 12 extends inwardlyinto the kiln beyond plate 16, and the outer end of the rod extendsoutwardly out of the kiln beyond plate 18.

Mechanism 10 includes mounting means for pivotally supporting rod 12intermediate the inner and outer ends thereof. The mounting meansconveniently comprises a coupler assembly 20 affixed to plate 18.Biasing means are provided for urging the inner end of rod 12downwardly. The biasing means conviently comprises a weight 22 affixedto rod 12 near the inner end thereof. Supporting means are attached toplate 16 and positioned below the inner end of rod 12 for holding thedevice of the invention in the path of downward movement of the innerrod end. The supporting means conveniently comprises a pair ofhorizontally separated, horizontally extending strips 24, only one ofwhich is shown in the drawing. A retaining means, such as a collarassembly 26, is attached to the outer end of rod 12.

A housing 28 is affixed to plate 18, and an actuating means isoperatively connected to the outer surface of the housing. The actuatingmeans conveniently comprises a pivotally mounted weighted arm assembly30. Arm assembly 30 includes an adjustably mounted plate 32 which isengageable by collar assembly 26 when the device of the inventionprevents the inner end of arm 12 from moving downwardly, and which isreleasable by collar assembly 26 when the device of the inventionpermits the inner end of arm 12 to move downwardly. Integrally affixedto the lower portion of arm assembly 30 is a projection 34. When plate32 is released by collar assembly 26, arm assembly 30 pivots downwardly,so that projection 34 enters an opening 36 formed in the outer surfaceof housing 28. Mounted within housing 28 is a switch (not shown) that iscontactable by projection 34 for interrupting the electrical heatingcircuit of the kiln. As will be apparent from this brief description,the movements of the various mechanical elements comprising mechanism 10are initiated by downward movement of the inner end of rod 12, and thelatter movement is controlled by the device of the invention. A detaileddescription of the structure and operation of mechanism 10 appears inthe aforementioned Dawson patent.

A first embodiment of the device of the invention is shown in FIGS. 1 3,and comprises a pyrometric member 40 composed of fusible ceramicmaterial. Member 40 is generally configured as a truncated rectangularpyramid having four longitudinally extending planar sides which taperinwardly from one end (the left end as seen in FIG. 2) to the other end(the right end as seen in FIG. 2) thereof. One of the sides of themember is adapted to contact strips 24 of mechanism 10 so that themember will be held in the path of downward movement of the inner end ofrod 12.

Member 40 has means for accurately regulating the amount of heatrequired to cause deformation of the member. Such means are comprised bya plurality of transversely extending notches 42 in the side of member40 opposite the side thereof adapted to be contacted by strips 24.Notches 42 extend entirely across the side of member 40, and when themember is held on strips 24, the inner end of rod 12 is engageable inone of the notches. Thus, lateral placement of member 40 with respect tostrips 24 and the inner end of rod 12 is accurately controlled bynotches 42.

In operation, member 40 prevents downward movement of the inner end ofrod 112 until the interior of the kiln has been exposed to apredetermined amount of heating. During heating, member 40 partiallyliquefies until the downward bending force applied to the mem ber by theinner end of rod 12 causes the member to deform, thus permitting theinner rod end to move downwardly to initiate the hereinabove describedmovements of the mechanical elements comprising mechanism 110.

The transverse cross-sectional area of member 40 is large enough topreclude premature deformation or fracture of the member, as frequentlyoccurs with conventional pyrometric cones.

Also, preferably, notches 42 and the portions of the side of member 40which contact strips 24, such portions being designated by referencenumeral 44, are coated with a refractory material, such as high alumina,zirconia or platinum, to prevent the ceramic material from which member40 is composed from adhering to the inner end of rod 12 or strips 24when the ceramic material liquefies during heating.

Member 40 may be composed of various ceramic materials or mixtures ofsuch materials to provide the desired deformation characteristics. Also,notches 42 permit controlled variations in the amount of heating whichmay be achieved utilizing a member of a particular composition andconfiguration.

A second embodiment of the device of the invention is shown in FIG. 4,and comprises a pyrometric member 50 composed of fusible ceramicmaterial. Member 50 has one longitudinally extending planar side 52which is adapted to contact strips 24. The portions of the exteriorsurface of member 50 other than side 52 are generally arcuately shaped.Other than differences in configuration, members 40 and 50 areidentical.

A third embodiment of the device of the invention is shown in FIG. 5,and comprises a pyrometric member 60 composed of fusible ceramicmaterial. Member 60 has a uniform rectangular transverse cross-sectiondefined by four longitudinally extending planar sides so thatirrespective of the lateral placement of the member on strips 24, apredetermined amount of heating will be required to cause deformation ofthe member. If desired, however, member 60 may have a transverselyextending notch 62 in one side thereof to facilitate placement of themember on strips 24. Also, if desired, notch 62 and the portions of theside of member 60 adapted to contact strips 24 may be coated with arefractory material to prevent the ceramic material from which themember is composed from adhering to the elements of mechanism ll uponliquefaction of the ceramic material.

A fourth embodiment of the device of the invention is shown in FIG. 6,and comprises a pyrometric member 70 composed of fusible ceramicmaterial. Member 70 is generally configured as a truncated rectangularpyramid similar to member 40 described above. Alternatively, member 70may be configured as a truncated wedge having four longitudinallyextending planar sides of which two opposite sides are tapered inwardlyfrom one end (the left end as seen in FIG. 6) to the other end (theright end as seen in FIG. 6) thereof.

The means for accurately regulating the amount of heating required tocause deformation of member 70 are comprised by a transversely extendingnotch 72 in one side of the member and a transversely extending notch 74in the opposite side of the member. Member may be placed on strips 24with either notch 72 or notch 74 facing upwardly to engage the inner endof rod 12. The transverse cross-sectional area of member 70 at thelongitudinal position of notch 74 is less than the transversecross-sectional area of the member at the longitudinal position of notch72. Therefore, a greater amount of heating will be required to causedeformation of the member when the inner end of rod 12 is engaged bynotch 72 than when the inner end of the rod is engaged by notch 74.However, the amount of heating required to cause deformation of themember when the inner rod end is engaged by either notch is accuratelyregulated due to the predetermined placement of the notches. When theinner rod end is engaged by notch 72, strips 24 are contacted by notch74 and a portion of the side of member 70 having notch 74 therein.Similarly, when the inner rod is engaged by notch 74, strips 24 arecontacted by notch 72 and a portion of the side of the member 70 havingnotch 72 therein. Preferably, notches 72 and 74 and the portions of thesides of the member which are adapted to contact strips 24, suchportions being designated by reference numeral 76, are coated with arefractory material to prevent the ceramic material from which member 70is composed from adhering to the elements of mechanism when the ceramicmaterial fuses.

As will be apparent, all of the embodiments of the device of theinvention are used in the manner described above with respect to member40. As will also be apparent, each embodiment of the device of theinvention has means, such as a uniform transverse cross-section ortransversely extending notches, for accurately regulating the amount ofheating required to cause deformation of the member comprising thedevice.

Configurations other than those of members 40, 50, 60 and 70 also may beemployed in the device of the invention. For example, the member mayhave a circular, semi-circular or semi-elliptical transversecrosssection.

From the foregoing description, it will be apparent that the device ofthe invention obviates the problems associated with the use ofconventional pyrometric cones in kiln shut-off mechanisms. The tedioustask of accurate lateral placement of such cones to achieve the desiredfiring characteristics is eliminated. Also, the device of the inventionis not subject to premature deformation or fracture. In addition,adherence of liquefied ceramic material to the elements of the shut-offmecha nism which contact the device is eliminated.

While the foregoing constitutes a detailed description of the preferredembodiments of the invention, it is recognized that variousmodifications thereof will occur to those skilled in the art. Therefore,the scope of the invention is to be limited solely by the scope of theappended claims.

I claim:

]l. A device for controlling a mechanism adapted to interrupt theelectrical heating circuit of a kiln, said mechanism being of the typeincluding a rod adapted to extend through a wall of a kiln with theinner end thereof extending into the kiln and the outer end thereofextending out of the kiln, mounting means pivotally supporting the rodintermediate said ends, biasing means urging said inner end downwardly,supporting means positioned below said inner end for holding said devicein the path of downward movement of said inner end, retaining meansattached to said outer end, actuating means engageable by said retainingmeans when said device prevents downward movement of said inner end andreleasable by said retaining means when said device permits downwardmovement of said inner end, and a switch contactable by said actuatingmeans for interrupting the electrical heating circuit of the kiln whensaid actuating means is released by said retaining means, said devicecomprising:

a pyrometric member composed of fusible ceramic material and havingmeans for accurately regulating the amount of heating required to causedefor mation of the member so that upon exposure of the member to saidamount of heating, the member will at least partially liquefy anddeform, permitting said inner end to move downwardly under the influenceof said biasing means, thereby causing said electrical heating circuitto be interrupted, said regulating means comprising at least onetransversely extending notch in at least one side of said member, saidnotch extending entirely across said one side, and said member having aplanar side thereof opposite said one side and contactable with saidsupporting means, said inner end being engageable by said notch toaccurately control the placement of the member with respect to saidsupporting means and inner end. 2. A device as recited in claim 1;wherein the transverse cross-sectional area of said member varieslongitudinally of the member; and wherein each of two opposite sides ofsaid member have at least one of said notches therein and the notch inone of said sides is longitudinally displaced with respect to the notchin the other of said sides so that when said inner end is engaged by oneof the notches a different amount of heating will be required to causedeformation of the member than when said inner end is engaged by theother of said notches.

3. A device as recited in claim 1, wherein the portions of said memberadapted to contact said supporting means and said notch are coated witha refractory material to prevent said ceramic material from adhering tosaid supporting means and inner end when the ceramic material liquefiesduring heating.

4. A device as recited in claim 1, wherein said member has arectangularly shaped transverse cross-section.

5. A device as recited in claim 1, wherein said member has at least apartially arcuately shaped transverse cross-section.

1. A device for controlling a mechanism adapted to interrupt theelectrical heating circuit of a kiln, said mechanism being of the typeincluding a rod adapted to extend through a wall of a kiln with theinner end thereof extending into the kiln and the outer end thereofextending out of the kiln, mounting means pivotally supporting the rodintermediate said ends, biasing means urging said inner end downwardly,supporting means positioned below said inner end for holding said devicein the path of downward movement of said inner end, retaining meansattached to said outer end, actuating means engageable by said retainingmeans when said device prevents downward movement of said inner end andreleasable by said retaining means when said device permits downwardmovement of said inner end, and a switch contactable by said actuatingmeans for interrupting the electrical heating circuit of the kiln whensaid actuating means is released by said retaining means, said devicecomprising: a pyrometric member composed of fusible ceramic material andhaving means for accurately regulating the amount of heating required tocause deformation of the member so that upon exposure of the member tosaid amount of heating, the member will at least partially liquefy anddeform, permitting said inner end to move downwardly under the influenceof said biasing means, thereby causing said electrical heating circuitto be interrupted, said regulating means comprising at least onetransversely extending notch in at least one side of said member, saidnotch extending entirely across said one side, and said member having aplanar side thereof opposite said one side and contactable with saidsupporting means, said inner end being engageable by said notch toaccurately control the placement of the member with respect to saidsupporting means and inner end.
 2. A device as recited in claim 1;wherein the transverse cross-sectional area of said member varieslongitudinally of the member; and wherein each of two opposite sides ofsaid member have at least one of said notches therein and the notch inone of said sides is longitudinally displaced with respect to the notchin the other of said sides so that when said inner end is engaged by oneof the notches a different amount of heating will be required to causedeformation of the member than when said inner end is engaged by theother of said notches.
 3. A device as recited in claim 1, wherein theportions of said member adapted to contact said supporting means andsaid notch are coated with a refractory material to prevent said ceramicmaterial from adhering to said supporting means and inner end when theceramic material liquefies during heating.
 4. A device as recited inclaim 1, wherein said member has a rectangularly shaped transversecross-section.
 5. A device as recited in claim 1, wherein said memberhas at least a partially arcuately shaped transverse cross-section.